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1.
Summary Sorption
behavior of Th and U on cation-exchange resins was investigated from nitric
acid medium by both batch and column methods. The cation-exchange studies
involved the sorption of UO 22+ and Th 4+ and
their cationic complexes onto Dowex 50Wx8 and Dowex 50Wx4 resins (50-100 mesh).
The batch data yielded a separation factor ( Kd,Th/ Kd,U)
value of >100 for the cation-exchanger, Dowex 50Wx4 at 1-2M HNO 3.
Separation of uranium from thorium was also carried out by column method in
nitric acid medium using cation-exchangers, Dowex 50Wx4 as well as Dowex 50Wx8.
While uranium elution was possible at 1M HNO 3, Th could be eluted
only at higher concentration of nitric acid (>6M). The stripped solution
emanating from a mixer settler employing di-2-ethyl hexyl isobutyramide as
extractant and feed solution similar to THOREX process comprising 350 mg/l U
and 380 mg/l Th in 0.75M HNO 3 was loaded on the column and the
decontamination factor value for U in the product was >1000.</p>
</p> 相似文献
2.
Summary Three
silylcellulosic derivatives with different substitution degree were examined as
sorbents for uranyl ions. The adsorption rate and capacity of cellulose and
modified cellulose were investigated in aqueous media, at various pH and
temperature values. The polymer - metal complexes of UO 22+
were characterized by infrared and electronic spectra, and thermogravimetry.
The thermal behavior of cellulose (C), trimethylsilyl - cellulose (tmsc, SD=
2.85) and triphenylsilyl - cellulose (TPSC1, SD=2.89 and TPSC2, SD
=2.70) and their complexes with
uranyl ions in atmospheric air has been studied between room temperature and
600 °C. The Coats-Redfern method was applied to estimate the kinetic
parameters. The results revealed that the complexation of C and TMSC with UO 22+
increases the thermal stability.</p>
</p> 相似文献
3.
Summary A
simultaneous determination of gamma and neutron fluences in a mixed neutron +
gamma field can be achieved by gamma-ray spectrometry, optimizing the
moderator-converter-detector assembly and measuring both the direct gamma-lines
and the neutron induced prompt gammas. For the prompt gamma-lines a combination
of high efficiency and low background is the goal, and it can be best achieved
if the gamma-energy is in the range above about 1 MeV up to 2.5 MeV. The
optimal moderator-converter thickness can be determined experimentally. Most
converter elements produce gamma-rays in the low energy range. If chlorine is
used as a converter, the 1164.7 keV peak and the 1950-1960 keV peaks seems to
be a good choice. A very practical material containing chlorine is PVC. It is
an efficient moderator, it is solid, common, and can be handled easily.</p>
</p> 相似文献
4.
Summary The
electrolytic reduction of U 3O 8 powder was carried out
using LiCl-Li 2O molten salt in a 20-kg U 3O 8
batch cell to verify the feasibility of the process. As the current passes the
cell, the decomposition of Li 2O and the reduction of U 3O 8
occur simultaneously in a cathode assembly and oxygen gas evolvs at the anode.
The results from a 20-kg U 3O 8 scale cell were compared
with data obtained from a bench scale cell. The results suggest a successful
demonstration of this process, exhibiting a reduction conversion of U 3O 8
of more than 99% in a batch.</p>
</p> 相似文献
5.
Summary A
simple pre-irradiation separation approach has been worked out for the
determination of traces of tellurium in high purity selenium followed by
neutron activation analysis (NAA) for the end determination of the analyte/s.
The difference in volatilities of these elements has been utilized for the
separation of the analyte from the matrix. The complete volatility of selenium
at ~600 °C was established using neutron activation analysis and selenium
radiotracer. Standard addition was used to validate the results. The proposed
method of separation of selenium prior to irradiation could make the
determination of tellurium possible and also improved the detection limit by
several folds.</p>
</p> 相似文献
6.
Two
methods capable of near complete recovery of technetium adsorbed on charcoal
are presented. The first involves liquid extraction of the technetium from the
charcoal by hot 4M nitric acid. An average recovery of 98% ( n=3) is
obtained after three rounds of extraction. The second method involves dry
ashing with air in a quartz combustion tube at 400-450 °C. This method yields
an average recovery of 96% ( n=5). Other thermal methods were attempted, but
resulted in reduced recovery and incomplete material balance.</p>
</p> 相似文献
7.
Summary 8-Hydroxyquinoline
in benzene, xylene, chloroform and toluene diluents was used to modify silica
gel as a solid phase extractant (SPE) for the sorption of Eu(III) in batch
extraction techniques. Influences of solid/liquid ratio, pH, metal ion
concentration, particle size and temperature were studied. The optimum initial
pH is 4.2, while the maximum sorption capacities for the prepared impregnated
resins in benzene, xylene, chloroform and toluene diluents are 18.52, 14.98,
14.79 and 5.94 mg . g -1, respectively. The sorption
process is found to be affected by both metal ion concentration and particle
size of the impregnated resin. Thermodynamic parameters for the sorption of
Eu(III) were determined and the reaction is found to be exothermic and spontaneous
with enthalpy-14.23
and-23.71
kJ . mol -1 for benzene and xylene as diluents. Release of
the element from the loaded solid particles into 0.01M HNO 3 is@85% and@53% from
8-HQ/benzene/silica gel and 8-HQ/xylene/silica gel.</p>
</p> 相似文献
8.
Summary The
uptake of indigenously synthesized amorphous stannic and zirconium phosphate
was assessed for, one of the important fission fragment, cesium from aqueous
solutions using a radiotracer technique. A virtual increase in sorptive
concentration (from 1.0 . 10 -8 to 1.0 . 10 -2
mol . dm -3) and pH (from 2.4 to 10.2) and temperature
(from 303 to 333 K) enhanced the uptake of cesium on stannic phosphate.
However, the extremely high degree of uptake of cesium on zirconium phosphate
was almost unaffected with the dilution beyond 10 -5 mol .
dm -3 and pH (i.e., from 2.4 to 10.2) and temperature (from 303 to
323 K). Irreversible uptake occurring for these solids follow the Freundlich
adsorption isotherm and the presence of several complexing agents viz.,
sulphate, phosphate, glycine and EDTA did not affect appreciably the uptake of
cesium on zirconium phosphate but it did affect for stannic phosphate system.
Both these solids showed good radiation stability towards a 11.1 GBq Ra-Be
neutron source having neutron flux ca. 3.2 . 10 6 n .
cm -2 . s -1 and associated with a nominalg-dose of ca.
1.72 Gy/h, at least for the uptake of cesium.</p>
</p> 相似文献
9.
Summary Potassium
nickel hexacyanoferrate, KNiFC, was incorporated in the porous matrix of
zeolites by successive impregnation with Ni(NO 3) 2 and</o:p></p>
K 4Fe
(CN) 6. 1 CFC and PFC exchangers were first prepared by
impregnating the potassium nickel hexacyanoferrate into the clinoptilolite and
the synthetic P zeolite, respectively. Ion-exchange isotherms and breakthrough
curves were plotted. Results showed that the CFC sorbent is suitable for
removal of Cs + where PFC is more suitable for Sr 2+.
Negative effect of Na + as a competing ion in these exchangers was
less than in the parent zeolites. Isotherm plots fitted the Langmuir equation.</p>
</p> 相似文献
10.
Summary Newly
produced fission track (FT), instrumental neutron activation analysis (INAA)
and micro-Raman spectrometry data have been used to characterize the classical
source areas of the Milos obsidians better and to check the provenance of
obsidian artefacts. The Bombarda-Adhamas and Demenegaki obsidians yielded
indistinguishable FT ages 1.57±0.12 and 1.60±0.06 My, respectively, in agreement with previous FT data. By
INAA analyses it was possible to discriminate between the three obsidian
sources on Milos: Bombarda-Adhamas, Demenegaki and A. Ioannes. Raman
spectroscopy has been found to be a valuable technique to gain a
chemico-structural characterization of a given obsidian population in terms of
dissolved water content and microlite distribution/composition.</p>
</p> 相似文献
11.
Summary Exploratory
experiments have been carried out to investigate the effects of gamma-radiation
on iodine aerosols under various chemical conditions. The results indicate that
iodide ions (I -) in aerosol can be readily oxidized to I 2
and HIO, and some iodide ions may be converted to organic iodine when organic
additives are present in the KI solution from which the aerosol is generated.
The results also suggest that the chemical transformation of irradiated iodine
aerosol depends on the chemical environment both carrier gas and iodide
solution.</p>
</p> 相似文献
12.
Summary The
extraction of protactinium with Aliquat 336 (methyl-tri-caprylyl ammonium
chloride) in toluene, cyclohexane and chloroform from HCl, HNO 3, H 2SO 4,
HClO 4, HF and mixed HCl-HF media was investigated by radioactive
tracer technique. Distribution ratios of protactinium between the aqueous
solution and the organic phase were determined as a function of shaking time,
concentrations of acid in aqueous solution phase, extractant concentration and
type of diluents in the organic phase. Aliquat 336 can almost quantitatively
extract protactinium from strong HCl solution. At the same time, small amounts
of HF in HCl solutions have a strong effect on Pa distribution.</p>
</p> 相似文献
13.
Summary Sand
filters are used in water treatment stations to remove particulate matter from
underground water, where iron and manganese are collected forming thin oxide
films. These oxides of iron and manganese adsorb radium from underground water.
Radium concentration increases in time on the filters, and consequently the
level of radioactivity increases in the station. The removal of adsorbed radium
on sand using inorganic acids was studied. Good efficiency of radium removal
was obtained by controlling different parameters like temperature, time, pH,
addition of competitive cations and anions. It was found that hydrochloric acid
is the best for radium removal from sand filters. Maximum removal obtained was
about 60% at 5M BaCl 2 and 2M HCl at 50 °C for 180-minute contact
time. Kinetic parameters of the removal process were studied and compared with
literature data.</p>
</p> 相似文献
14.
Summary The
bioaccumulation of 198Au radionuclide, by Rhizoclonium riparium
a member of Chlorophyceae has been studied. It has been observed that
accumulation of gold on Rhizoclonium is almost pH independent and
slightly higher at basic pH. Accumulation of gold was studied with 198Au
radiotracer, 0.1, 1 and 5 ppm concentrations of gold. It has been concluded
from the biochemical analysis that the gold accumulation is due to adsorption
in the cellulose and not in protein, fat and carbohydrate. Accumulated gold was
recovered when washed with conc. HNO 3.</p>
</p> 相似文献
15.
Summary A
rapid method was developed using ultrafilters with a tangential flow filtering
system for molecular size separation of naturally occurring 210Pb
and 210Po in a freshwater sample. Generally, ultrafiltering of a
large volume water sample for measuring the nuclides was too time consuming and
not practical. The tangential flow filtering system made the filtering time
short enough to adapt for in-situ ultrafiltering the large volume sample. In this
method, a 20 liter water sample was at first passed through the 0.45mm pore size
membrane filter immediately after sample collection to obtain suspended
particle matter [>0.45mm particulate fraction (PRT)]. Two ultrafilters (Millipore
Pellicon 2 ò)
were used sequentially. The nuclides in the filtrate were separated into three
fractions: high molecular mass (100 kDa-0.45mm; HMM), low molecular mass (10 k-100 kDa;
LMM) and ionic (<10 kDa; INC) fractions. It took 80 minutes to process the
sample after collection. The cut-off molecular size of each ultrafilter was
confirmed by size exclusion chromatographs (SEC) of the LMN and the HMM
fractions. Adsorption of the nuclides and organic compounds in the sample onto
the ultrafilters was negligibly small. Good reproducibility of the nuclide
concentrations in each fraction was confirmed by repeated experiments. The
method was successfully applied to obtaine the molecular size distributions of 210Pb
and 210Po in an oligotrophic lake, Lake Towada located in the northern
area of Japan.</p>
</p> 相似文献
16.
Summary During
the period of 1993-2001 chemical decontaminations of 24 SGs in the units 1-3 of
the Paks NPP were carried out by a non-regenerative version of AP-CITROX
technology, even in two or three consecutive cycles. A comprehensive
investigation of the above decontamination method have revealed that the
fundamental issues of analytical chemistry and corrosion science were not taken
into consideration during the elaboration of AP-CITROX procedure. Therefore,
the non-regenerative version of the technology utilized at Paks NPP can be
considered to be not an adequate method for the chemical decontamination of any
reactor equipments having large steel surfaces (e.g., SGs). As a consequence of
the lack of the appropriate decontamination method, initiation of a R&D project
focused on the elaboration of the required technology should not be postponed.
In this paper, we present a brief overview on the fundamental issues of the
technology development . Selected findings obtained in our laboratory on
the field of the improvement of the AP-CITROX technology are also reviewed in
order to demonstrate the crucial role of some selection criteria.</p>
</p> 相似文献
18.
Polymeric matrices composed of N,N′-Methylenebis(acrylamide)/glycidyl methacrylate was prepared and modified producing two resins (GMA/MBA/OH and GMA/MBA/SO3H). The adsorption of U(VI) ions onto the modified acrylamide resins was studied from synthetic and granite samples. For better understanding around the uranium mineralization and the rock-forming minerals of the hosted granitic rocks, to facilitate the choice of the appropriate ore-processing techniques, it was necessary to identify the mineral composition and the radiometric specifications of the used granitic rock. The synthesized adsorbents revealed a promising selective adsorption toward the U(VI) ions from its bearing solutions even with the competence of other cations. 相似文献
19.
Summary Samples
of limestone, sand, marble, clay brick, red brick, gypsum, Portland cement and
white cement collected from upper Egypt used in building manufacturing have
been analyzed for the natural radionuclides 226Ra, 232Th and 40K usingg-ray
spectrometry. The specific concentrations for 226Ra, 232Th and 40K, ranged from 20-88,
13-115 and 54-304 Bq/kg, respectively. The average specific activities of these
radionuclides were compared. Higher values of 226Ra and 232Th could be noticed in marble while that of 40K
was in red bricks. Radium equivalent activities, dose rate and the annual
gonadal dose equivalents AGDE were calculated for the measured samples to
assess the radiation hazard arising from using those materials in the
construction of dwellings. The radioactive heat production values of the
selected materials have also been determined. They vary from a minimum of 0.41
for white cement to a maximum of 5.52mW/m 3 for
marble samples. The calculated heat-production values are quite similar to
those estimated in Corsica.</p>
</p> 相似文献
20.
The
reliability of an 90Sr determination method was tested using an Sr
extraction chromatographic resin for strontium isolation. The 90Sr-content
in samples of vegetables, soil and water (obtained from Environmental
Measurement Laboratory, USA) were determined and the results were controlled by
classical methods and by using an anion-exchanger and an alcohol solution of
nitric acid for the strontium isolation. These methods were previously tested
by determining 90Sr in IAEA 326 and 327 samples of soil. It is shown
that the isolation process with Sr resin is simpler and faster than the
classical and mixed solvent anion-exchange methods. The efficiency of isolation
on a Sr column depends on the resin quantity and separation conditions; and is
the highest with a Sr column, compared to the classical and anion-exchange
methods. Experimental data and theoretical models were used to calculate the
parameters that enable the estimation of optimum dimensions of the column for
isolation. A simple relation is proposed for the calculation of breakthrough
volume, which defines the sample and eluent volumes for an optimal strontium
isolation.</p>
</p> 相似文献
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